bug#18246: enriched-encode: should set inhibit-point-motion-hooks, too

[Ivan Shmakov]

Package:  emacs

        While enriched-encode already sets inhibit-read-only to t to
        avoid issues with any text bearing the read-only property [1] in
        the encoded part, it doesn’t yet set inhibit-point-motion-hooks,
        which easily results in incorrect encoding should text being
        encoded contain parts protected with the ‘intangible’ property.

        Example:

(with-temp-buffer
  (insert "Hello, world!\n")
  (re-search-backward "\\<")
  (put-text-property (point) (point-max) 'intangible t)
  (put-text-property (+ -1 (point)) (+ 1 (point)) 'face 'bold)
  (put-text-property (+  2 (point)) (+ 3 (point)) 'face 'italic)
  (enriched-encode (point-min) (point-max) nil)
  (buffer-substring-no-properties (point-min) (point-max)))
"Content-Type: text/enriched
Text-Width: 72

Hello,<bold> <</bold>italic>world!
</italic>"

        With the trivial patch MIMEd, this results in the following
        (correct) string instead:

"Content-Type: text/enriched
Text-Width: 72

Hello,<bold> w</bold>o<italic>r</italic>ld!
"

[1] 
http://www.gnu.org/software/emacs/manual/html_node/elisp/Special-Properties.html

-- 
FSF associate member #7257  http://boycottsystemd.org/  … 3013 B6A0 230E 334A

--- a/lisp/textmodes/enriched.el
+++ b/lisp/textmodes/enriched.el
@@ -314,7 +314,8 @@ the region, and the START and END of each region."
 ;;;###autoload
 (defun enriched-encode (from to orig-buf)
   (if enriched-verbose (message "Enriched: encoding document..."))
-  (let ((inhibit-read-only t))
+  (let ((inhibit-read-only t)
+       (inhibit-point-motion-hooks t))
     (save-restriction
       (narrow-to-region from to)
       (delete-to-left-margin)